Abrasive



Feb. 1, 1944. w, 5; E Y I 2,340,504

ABRASIVE Filed March 1. 1943 an, v w

- ATTORNEY.

Patented Feb. 1, 1944 UNITED STATES PATENT orrlca William E. Bcatty, Hollywood, Calif. Application March 1, 1943, Serial No. 477,614 Claims. (01. 51-293) The invention relates to an improvement in abrasives, such as carbonmdum wheels'or saws,

emery cloth or paper and the like.

Carborundum wheels about one-sixteenth of an inch thick and about nine or ten inches in diameter, are commonly used to out steel rod or the'like. Such wheels manufactured by the Carborundum Company and known as resinoid while commonly used to a large extent, have a serious drawback in that they are very fragile. For examp e, if such a wheel is held at one edge by the is sprayed on a matrix which may be smooth or rough and the coating thus produced is stripped from the matrix and the resulting sheet is treated to render it translucent and suitable for the projection of the pictures. a

According to the present invention, I make use of such a coating composition, although in itspreferred form I add to it a suitable percent of resin as will be described later. This coating composition is applied to the carborundum wheels above described now on the market, by

thumb and forefinger and it is tilted or swung slowly through the air, the chances are that the wheel will break. Many of them are broken in shipping and many others are broken in the course of trying to clamp them on the spindle.

Also the periphery of such a wheel soon becomes jagged and as a jagged edge is liable to fracture the whole wheel when in use, it is common to discard such wheels after a short period of use and when they are still abouteight inches in diameter.

It is assumed wheels of the particular type dipping, brushing or spraying, preferably the latter.

It has been discovered that such wheels are so porous that if the coating composition with.

suflicient thinner, is sprayed on one side of the wheel when it is supported flat, the coating composition will leak through the pores of the wheel, coat the channels through it as well as the opposite surface. The wheel thus coated may be airdried or drying may be hastened by heating in an oven at about 250 F. for about ten minutes mentioned above comprise a plurality of different sizes of crystals of carborundumpressed in the shape of a wheel with a suitable binder. At any rate, the binder employed in such wheels as now available on the market results in a very brittle and fragile wheel, as pointed out above.

Aside from the above disadvantages in the use of such a wheel, a considerable amount of time is lost in the normal use of the wheel, for the reason that it is customary to try to avoid breaking the wheel when in use by bringing it lightly to the work then backing it off, waiting a while, then bringing it to the work again, commonly known as dancing the wheel on the work. Hence, the actual time that the wheel is in contact with the work forms only a small part of the total time consumed in cutting a-steel rod.

7 An object of the present invention is particularly directed to increasing the strength of such wheels and this has led to the extension of the idea into analogous fields such as emery cloth or paper.

The following U. S; Patents 2,071,342, 2,133,076, 2,216,901 and 2,257,999 disclose the use of various coating composition 'for the manufacture or translucent motion picture projection screens. Generally speaking, the coating composition may comprise cellulose acetate, or nitrate or ethyl cellulose, or benzyl cellulose, and a plasticizer, dissolved in a solvent. The above patents disor more.

The result is that the coating composition forms a binder which interlocks all of the abrasive particles of the wheel together, and increases the strength and life of the wheel.

A preferred binder comprises ethyl cellulose in flake form, with a plasticizer such as triphenolphosphate or the like, plus a resin such as taglac or beckacite, the latter being a phenolic resin,

" plus a solvent which may be one or more of the following: methyl alcohol, butyl alcohol, butyl acetate, and hydrocarbons such as toluol, benzol,

' and zylol.

While the above mentioned resin by itself is brittle, and no doubt this property i of advantage in holding the abrasive particles of the wheel together in their proper shape, by using from zero to of the solids as one or more of the above resins, I still obtain a binder which is not brittle, .but if it were applied to a fiat matrix and stripped off as in screen manufacture, it would close various formulae which may be employed.

The coating composition for screen manufacture,

be found that the coating would be flexible and could be bent back and forth many times without cracking.

The characteristics .of the preferred binder above mentioned are that it absorbs only a small amount of water, such as 2%, which is less than is true of some of the other cellulose compounds mentioned above. Also, a film of the preferred binder is very strong, as a film .001 of an inch thick will stand a pressure of about thirty pounds per square inch. The per cent of resin in the preferred binder could be increased to about 50% 2 l 2,340,504 of the solids and the resulting film would still be abrasive particles, and hence it readily wears flexible. The resin increases the toughness of 1 away when the abrasive is moved acrossthe surthe film. face of the work piece.

Another advantage of the preferred binder is For further details of the invention reference that it retains its flexibility, strength and tenacity may be made to the drawing wherein Fig. 1 'is a at temperatures as low as 70 0. below zero, and plan view of a wheel coated according to the hence it does not become brittle in ordinary cold present invention.

weather. Fig. 2 schematically illustrates a support for A carborundum wheel as above described, the wheel to be coated.

of an inch thick, and known as resinoid, after Fig. 3 is a greatly magnified sectional view on having been discarded by a machine shop as line 3-3 of Fig. 1, illustrating schematically the being unfit for further use, although its periphgeneral arrangement of the coating composition ery was not particularly jagged, was treated with as applied to a carborundum wheel one-sixteenth the preferred binder above mentioned, using 10% of an inch thick.

resin, the binder solution was transparent, it Referring to the' drawing, the wheel I illuswas sprayed on one side of the wheel while it was trates the carborundum wheel above described supported in a horizontal position on a flat suras now available on the market and having a face, the sprayed material seeped through the central aperture 2, and the plastic coating or wheel to the underside thereof, and the wheel binder of this invention is indicated at 6.

thus coated was put in an oven and baked at no In Fig. 2, 2 illustrates a base on which the 250 F. for ten minutes. The wheel thus treated wheel I may be supported when it is sprayed or was stronger and more rigid than the untreated brushed with the above described coating com-- wheel. Its appearance to the eye of a casual position. The wheel i. may be dipped in the observer was practically unchanged, because the composition if desired. coating compositionds transparent and so near 2 in Fig. 3, an attempt is made to schematically as can be determined a film approximately only illustrate what apparently happens when the .001 or .002 of an inch thick appeared on the op-' w l is spray d with th ati mat ri as posite sidesof the wheel, although it may have found in the test above described. The carborunbeen much thicker than this in the interior pores dum crystals are indicated by the reference numof the wheel. The wheel felt slightly smoother her These y a are a the Present time to the touch and it still showed the usual rough pp y held tog her by a b d r 9, which 18 surface on both sides thereof. It was heavier in Suppo ed t be re i In ny n it is ve y weight showing that the binder had loaded t brittle with the defects above noted. The plastic Wheel. The wheel: thus treated was tested. by atin and b din mp sition f this nv napplying constant pressure to the wheel while it 3 tion is illustrated by the portion 6 which is on was employed to cut steel rod and it cut straight one side of the wheel, this coat ng comp through without breaking, whereas this operation seeps thr Whatever channels i finds between is not possible, or at least not practiced univere c y tals 5, O e u h channel being p sally, with an untreated wheel. Also the wheel Sented at and finds its W y through the interthus treated was able to cut straight through a 4 stices of the crystal 5 t0 he pp it Side Where drill about one-half inch in diameter by cont fo s th coat n If desired, however, the stantly keeping the wheel in' contact with the at hg e l s uld b m de a lo thicker drill, it not being necessary to repeatedly and so that it would not flow through so that itcould lightly bring the wheeltothe work as heretofore. be sprayed on opposite sides, but this is not Thus the work can be done in about one fourth it necessary if-suflicient olve i e p oye make of the usual time. it approximately of the consistency of rather The coating and bindingcompositions as above thin Sugar y p- It will be-appar n therefore.

described may also be used for other types of that the abrasive particles 5 of the wheel I are abrasives. It has been applied to the abrasive interlocked with a Plastic bind r whi h h great side of emery cloth. The coating composition ength even i thin film whi m taken seeped through the abrasive and coated the fabby itself is. flexible as distinguished from brittle. riclbeneath, The result-was that some of the If the coating solution is then enough, i. e. like valleys in the abrasive side were fllled up with thin sugar syrup, the channels such as I may'in the binder, the binder held the abrasive particles fact in the above test have been coated. with a together and to the. cloth, and the cloth thus hollow tubular film of the plastic binder in t ad coated was flexible and very much stronger and of solid threads as shown in Fig. 3, or both tubes tougher thanheretofore. The result of fillingu and threads. In any event, after using the some of the valleys in theabrasive is to preven treated wheel above described for cutting a large making deep scratches when using the cloth, number of steel pieces, the cutting edge of the whereby a more uniform polishing effect is obwheel was examined and found to contain a large tained. number of voids or hollows or depressions and i s The binder composition above described may granular appearance was no diflerent to the also be applied to sandpaper and to sand belts, naked eye than an untreated wheel. The peby applying a coating thereof to the abrasive riphery was less jagged,.if anything, than before.

side, or to the backing side, or to both. This All the interstices between the grains 5 were not coating composition makes the backing more filled up with the film 6 which was very thinflexible and hence a sanding belt will conform a few thousandths of an inch thick-and this is more readily to the driving pulleys and reduce desirable because it leaves depressions to reduce the slippage which is encountered with the comloading up as with untreated wheels, and faciliparatlvely stiff backings. tates the wheel to wea away when cutting soft While the binder composition above described metal such as dural, without burning the work.. imparts considerable strength and body to the If desired however, multiple coats with drying or abrasive, whether in the form of a wheel or havbaking between each coat may be used until all ing a backing of cloth or paper or both or the the pores are filled and the abrasive particles are like, this binder is very much softer than the entirely encased in the plasticbinder.

.and before it solidifies,

Also the use of the wheel in the above test did not result in any apparent stripping of the films 6 and 8 from the sides of the wheel, due no doubt to the interlocking of those films with the grains 5. The melting point of the material of films or coating 6 and 8, after the liquid coating has dried and solidified, is about 450 F. When the wheel I is cutting a work piece, if this temperature is approached, which seems unlikely, the coating 6 and 8 and in channels I would soften to facilitate breaking away the grains 5. At normal working temperatures, the binder of this invention has great strength, even in thin films. If desired, the coating composition can be applied only to the backing of paper or cloth'for the abrasive particles. In fact it can be applied to the bac 'ng material per se, and the abrasive particles can be later with any suitable binder. Multiple coats can be used with drying or be g between successive coats. The backing thus produced is flexible, and

very strong. Abrasive particles can be applied thereto in any suitable manner. As a later application of the liquid coating to a former dried film thereof will coalesce therewith due to the volatile solvent in the fresh liquid coating, a liquid coating of this material forms an excellent binder for abrasive particles to be cemerited to a coated backing as above suggested.

,Also the coating in liquid form may be applied,

viz., sprayed on the underside of a fabric and-as the coating impregnates the fabric and oozes to the top of the fabric, 'while it is still wet or tacky, abrasive particles may be sprinkled on the wet plastic on top of the fabric whereby the abrasive particles form facets in a solidified setting of the film or binder when it sets. Or, the liquid coating may be applied to the top of paper or fabric and the abrasive particles spread or sprinkled thereon before it sets. Multiple coats of the liquid binder and abrasive particles may thus be built up on the backing if desired.

One or multiple coats of the film 6 and 8 around the aperture 2 is desirable as such films not only strengthen the wheel but form in eifect integral washers which are flexible and which further reduce the likelihood of the wheel I breaking when it is clamped on its driving spindle. If the coating solution is sprayed or applied to the top. side of wheel I while resting on a flat support 4, the film on the underside of the wheel will have a flat surface, thereplica of the support, if an excess of the coating solution is used. This is deapplied and bound thereon sirable adjacent the aperture 2 and can be used throughout the whole of the side of the wheel, but has not been found necessary.

To preventthe solution from adhering to support 4, it should be noncompatible with the solution and may be of the nature set forth in the above patents or others of the same patentees, although other materials may be used.

As the dried films 6 and 8 are very thin and transparent, the marking and label on the untreated wheel are just as visible after the wheel has been treated. However, to distinguish a treated from an untreated wheel, the coating solution may have a suitable dye or, color added to it. I

I claim:

1. The process which comprises interlocking abrasive particles by applying thereto a solution of ethyl cellulose.

2. The process which comprises interlocking abrasive particles by applying thereto a solution of ethyl cellulose, a plasticizer and resin, the amount of resin being less than about 50% and insuificient-to form a brittle film.

3. In an abrasive device having abrasive particles held by a hinder. the improvement which comprises a coating of plastic flexible filmforming material on said particles and binder, said boating comprising ethyl cellulose, synthetic resin and a plasticizer.

4. The process of adding a secondary binder to a preformed porous abrasive article having abrasive particles secured by a primary binder, said process comprising supporting the abrasive article in a horizontal position on a matrix and applying a liquid solidifiable binder to the article, said binder comprising a solution of ethyl cellulose, a plasticizer and synthetic resin the binder being thin enough to seep through the pores of the article and flow on the matrix, allowing the article thus coated to set, and stripping the same from said matrix. 5. The process of reinforcing a thin porous abrasive disc which comprises supporting said disc in a horizontal position on a matrix, and applying on said disc a liquid binder comprising a solution of ethyl cellulose, a. plasticizer and synthetic resin, said solution being thin enough to impregnate said disc and seep through the pores of said disc and flow on the allowing the coating thus formed on the disc to set and stripping the coated disc from said matrix.

WILLIAM E. BEATTY.

matrix under said disc, 

